Total glass area: 180 sq ft
Annual Savings
$307
per year estimated
Monthly Avg
$26
per month
10-Year Total
$3,068
cumulative
Payback
26.4
years to recoup
940 lbs
CO2 reduced
7.8
trees planted equiv.
1,166
miles not driven
| Specification | Current | Upgrade | Change |
|---|---|---|---|
| U-Value (BTU/hr-ft2-F) | 1.10 | 0.30 | 73% better |
| SHGC | 0.86 | 0.27 | 69% lower |
| R-Value | 0.91 | 3.33 | +266% |
| Visible Transmittance | 0.90 | 0.51 | Good |
| STC (Sound) | 26 | 31 | +5 |
| UV Blocking | 25% | 95% | +70% |
| Weight (lbs/ft2) | 1.6 | 3.4 | Heavier |
Federal: IRA Energy Efficient Home Improvement Credit
Up to 30% of the cost of qualifying windows, max $600/year. ENERGY STAR Most Efficient certification required.
Learn more at ENERGY STAROur energy specialists will evaluate your windows on-site and provide a detailed savings estimate tailored to your home.
Licensed and insured -- Fully Insured -- Same-week appointments available
Methodology
Our calculator uses the same physics-based approach as the Department of Energy and ENERGY STAR to model heat transfer through your windows.
Calculated using U-value differentials and monthly Heating Degree Days (HDD) for the Washington DC metro area (total ~4,350 HDD/year). Lower U-values mean less heat escapes through your windows in winter, reducing furnace runtime and gas consumption.
Calculated using Solar Heat Gain Coefficient (SHGC) differentials and monthly Cooling Degree Days (CDD) for the DMV (~1,800 CDD/year). Lower SHGC means less solar heat enters your home in summer, reducing air conditioning costs.
We factor in your home age (older homes have more air leakage around window frames), window orientation (south and west-facing windows receive significantly more solar radiation), and HVAC system efficiency (heat pumps vs gas furnaces have very different energy economics).
Energy costs are calculated using actual utility rates from your local provider -- Dominion Energy, Pepco, or BGE. Heating costs use natural gas rates (therms) while cooling costs use electricity rates (kWh), reflecting how most DMV homes actually consume energy.
Education
Measures how well a window insulates. It represents the rate of heat transfer through the glass assembly. The lower the U-value, the better the insulation.
Measures how much solar radiation passes through the window. In hot climates like DMV summers, lower SHGC reduces cooling costs. Ranges from 0 to 1.
Measures how much visible light passes through. Higher VT means brighter rooms. Low-E coatings reduce some visible light while blocking much more heat.
The inverse of U-value (R = 1/U). Measures resistance to heat flow. Higher R-value means better insulation. Familiar from wall insulation ratings.
FAQ
Our calculator uses DOE-standard thermal formulas with actual DMV climate data (Heating and Cooling Degree Days), local utility rates, and physics-based heat transfer modeling. However, actual savings vary based on installation quality, home insulation, air sealing, HVAC condition, and individual usage patterns. These estimates are best used for comparison and planning purposes. For a precise assessment, we recommend our free on-site energy evaluation.
Low-E (low-emissivity) glass has a microscopically thin metallic coating that is invisible to the eye. This coating reflects infrared heat while allowing visible light through. In summer, it reflects solar heat away from your home. In winter, it reflects your interior heat back inside. This dual action makes Low-E glass significantly more efficient than standard clear glass, typically reducing solar heat gain by 60-70% while only reducing visible light by 20-30%.
For most DMV homes, Low-E double pane glass offers the best value -- significant energy savings at a moderate cost with a reasonable payback period. Triple pane is worth considering if you have large picture windows, live in a particularly drafty older home, value maximum noise reduction, or plan to stay in your home for 15+ years. The DMV climate is moderate enough that triple pane is a premium choice rather than a necessity.
Yes. The federal Inflation Reduction Act (IRA) offers a tax credit of 30% of the cost of qualifying energy-efficient windows, up to $600 per year. Windows must meet ENERGY STAR Most Efficient criteria. Additionally, local programs through Dominion Energy, DCSEU, and EmPOWER Maryland may offer additional rebates. We recommend consulting a tax professional for your specific situation.
Quality double and triple pane windows typically last 20-30 years before the seals begin to degrade. Low-E coatings do not wear off or degrade under normal conditions. The argon gas fill between panes slowly leaks at about 1% per year, so after 20 years, windows still retain approximately 80% of their original insulating gas. Proper installation is key to maximizing window lifespan.
Electricity and gas rates vary significantly between DMV utility providers. Dominion Energy (Virginia), Pepco (DC), and BGE (Maryland) each have different rate structures. Since heating primarily uses natural gas and cooling uses electricity, the ratio between your gas and electric rates directly affects which improvements save you the most money. Using your actual provider rates gives you a more accurate savings estimate.
Expert Glass Repair -- Serving the DMV
Our energy specialists will evaluate your windows on-site and provide a detailed savings estimate tailored to your home. No obligation, no pressure.
Licensed and insured -- Fully Insured -- Same-week appointments available
This energy savings calculator is provided as a complimentary visualization and planning resource to help you explore design options and understand approximate configurations for your glass project. All dimensions, specifications, performance calculations, and visual representations displayed are estimates intended for planning purposes only and should not be used as final construction measurements or guaranteed performance values.
Accurate field measurements and assessments by a licensed glass technician are required before any fabrication, installation, or purchasing decisions. Site conditions, structural factors, building codes, and environmental variables can significantly affect final specifications and product selection.
Expert Glass Repair provides complimentary on-site assessments and professional consultations throughout the DC, Northern Virginia, and Maryland metro area. For precise specifications and a free estimate, contact our team at (703) 679-7741.